The invention relates to a reflector for dental and surgical operating room lighting fixtures and the like.
The combination of ellipsoid and paraboloid (for example, DE No. 24 46 521, U.S. Pat. No. 3,191,023) reflectors in the case of the customary use of an elongated light source, especially an incandescent filament, in principle offers the possibility of producing an elongated light field in a desired working place spaced a distance from the light source. This represents a significant advantage in comparison with reflectors in the form of an ellipsoid section (U.S. Pat. Nos. 3,511,983, 4,149,227) or a paraboloid section (U.S. Pat. No. 4,459,647). However, it is difficult for the usual applications, for example, in the jaw area, to achieve a sufficiently great elongated light field and in it a desired uniform beam power density, specifically over a depth necessary for use (in the direction of the optical axis y=0, z=0 of the reflector). To approach this goal, it is known to modify the shape of the reflector. Thus, an ellipsoid reflector is known (U.S. Pat. No. 3,511,938), whose basic ellipsoid shape is overlaid with a plurality of convex or concave partial mirrors. Production of such a re lector is quite expensive. In another known ellipsoid reflector (U.S. Pat. No. 4,149,227), the ellipsoid is made up of strip-shaped segments that are twisted somewhat outward. This method of construction is also very expensive. The same applies for another known reflector (U.S. Pat. No. 4,459,647), which has the shape of a paraboloid section wherein the parabolic surface is made up of plane mirror segments.
Generally, the subdivision of the reflector into several partial surfaces has the drawback that it is not possible to deposit thin layers with uniform thickness by vapor. Thus, specially in the usual vapor deposition of thin reflecting layers, chromatic distortions occur within and especially on the edges of the light field. Finally, the assembly from partial surfaces in reflectors with the initially mentioned basic shape of an ellipsoid-paraboloid section is still more expensive than with simpler basic shapes.
In a known reflector of the initially indicated type (J. G. Holmes, Lighting Research and Technology, 1979, Volume 11, No. 2, pages 95-98), the ellipsoid-paraboloid basic shape in which a parabolic or elliptic shape is present in two axial planes perpendicular to one another, is formed in the transition areas between these axial planes so that all plane sections perpendicular to the ellipse plane are parabolas, and all beams that emerge from the closer ellipsoid focal point and the paraboloid focal point united with it, are reflected parallel to the ellipse plane and go through a focal line of the more distant ellipse focal point perpendicular to the ellipse plane. Thus, a wider light field containing the focal line can be illuminated only with very great irregularity of the beam power density. References to other possible intensity distributions are contained in this work, but only one of them corresponds to the effort to obtain a wider light field with uniform illumination; for this purpose, a double ellipsoid is proposed, which has different closer focal point distances in two axial sectional planes perpendicular to one another. It is clear that thus the ellipsoid paraboloid concept was abandoned.